Section 250-RICR-120-05-27.11 - Equipment Tuning ProcedureA. This tuning procedure, based on a tune-up procedure developed by KVB Inc. for the EPA, in §§ 27.11(A)(1) through (10) of this Part, shall be followed 1. Operate the unit at the firing rate most typical of normal operation. If the unit experiences significant load variations during normal operation, operate it at its average firing rate.2. At this firing rate, record stack gas temperature, oxygen concentration and CO concentration (for gaseous fuels) or smoke-spot number (for liquid fuels) and observe flame conditions after the unit stabilizes at the firing rate selected. If the excess oxygen in the stack gas is at the lower end of the range of typical minimum values, and if the CO emissions are low and there is no smoke, the unit is probably operating at near optimum efficiency - at this particular firing rate. However, complete the remaining portion of this procedure to determine whether still lower oxygen levels are practical. a. The smoke-spot number can be determined with ASTM Test Method D- 2156-09, incorporated in § 27.4(B) of this Part, or with the Bacharach method. ASTM Test Method D- 2156-09 is included in a tune-up kit that can be purchased from the Bacharach Company.b. Typical minimum oxygen levels for boilers at high firing rates are: (1) For natural gas: 0.5% - 3.0%(2) For liquid fuels: 2.0% - 4.0%3. Increase combustion air flow to the furnace until stack gas oxygen levels increase by one to two percent over the value measured in § 27.11(B)(2) of this Part. As in § 27.11(B)(2) of this Part record the stack gas temperature, CO concentration (for gaseous fuels) or smoke-spot number (for liquid fuels) and observe flame conditions for these higher oxygen levels after boiler operation stabilizes.4. Decrease combustion air flow until the stack gas oxygen concentration is at the level measured in § 27.11(B)(2) of this Part. From this level gradually reduce the combustion air flow in small increments. After each increment, record the stack gas temperature, oxygen concentration, CO concentration (for gaseous fuels) and smoke-spot number (for liquid fuels). Also, observe the flame and record any changes in its condition.5. Continue to reduce combustion air flow stepwise until one of these limits is reached: a. Unacceptable flame conditions - such as flame impingement on furnace walls or burner parts, excessive flame carryover or flame instability.b. Stack gas CO concentration greater than 400 ppm.d. Equipment related limitations - such as low windbox/furnace pressure differential, built in air flow limits, etc.6. Develop an O2/CO curve (for gaseous fuels) or O2/smoke curve (for liquid fuels) similar to those in Figures 1 and 2 using the excess oxygen and CO or smoke-spot number data obtained at each combustion air flow setting.7. From the curves prepared in § 27.11(B)(6) of this Part, find the stack gas oxygen levels where the CO emissions or smoke-spot number equal the following values: Fuel | Measurement | Value |
Gaseous | CO emissions | 400 ppm |
#1 & #2 oils | Smoke-spot number | Number 1 |
#4 oil | Smoke-spot number | Number 2 |
# 5 oil | Smoke-spot number | Number 3 |
# 6 oil | Smoke-spot number | Number 4 |
The above conditions are referred to as CO or smoke threshold, or as the minimum excess oxygen level.
Compare this minimum value of excess oxygen to the expected value provided by the combustion unit manufacturer. If the minimum value found is substantially higher than the value provided by the combustion unit manufacturer, burner adjustments shall be made to improve fuel and air mixing, thereby allowing operation with less air.
8. Add 0.5 to 2.0 percent to the minimum excess oxygen level found in § 27.11(B)(7) of this Part and reset burner controls to operate automatically at this higher stack gas oxygen level. This margin above the level accounts for fuel variations, variations in atmospheric conditions, load changes and non-repeatability or play in automatic controls.9. If the load of the combustion unit varies significantly during normal operation, repeat §§ 27.11(B)(1) through (8) of this Part for firing rates that represent the upper and lower limits of the range of the load. Because control adjustments at one firing rate may affect conditions at other firing rates, it may not be possible to establish the optimum excess oxygen level at all firing rates. If this is the case, choose the burner control settings that give the best performance over the range of firing rates. If one firing rate predominates, settings should optimize conditions at that rate.10. Verify that the new settings can accommodate the sudden changes that may occur in daily operation without adverse effects. Do this by increasing and decreasing load rapidly while observing the flame and stack. If any of the conditions in § 27.11(B)(5) of this Part result, reset the combustion controls to provide a slightly higher level of excess oxygen at the affect firing rates. Next, verify these new settings in a similar fashion. Then make sure that the final control settings are recorded at steady state operating conditions for future reference.B. Nothing in this Equipment Tuning Procedure shall be construed to require any act or omission that would result in unsafe conditions or would be in violation of any regulation or requirement established by Factory Mutual, National Fire Prevention Association, the Rhode Island Department of Labor (Division of Occupational Safety), the Federal Occupational Safety and Health Administration or other relevant regulations or requirements.250 R.I. Code R. 250-RICR-120-05-27.11
Amended effective 12/26/2018